"A treaty can't authorize what the Constitution doesn't."
Says who? You?! Sez the Supreme Court:
The treaty power, as expressed in the constitution, is in terms unlimited, except by those restraints which are found in that instrument against the action of the government, or of its departments, and those arising from the nature of the government itself, and of that of the states. It would not be contended that it extends so far as to authorize what the constitution forbids, or a change in the character of the government, or in that of one of the states, or a cession of any portion of the territory of the latter, without its consent. - Geofroy v. Riggs, 133 U.S. 258 (1890)
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Article VI, the Supremacy Clause of the Constitution, declares:
"This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land; . . . ."
There is nothing in this language which intimates that treaties and laws enacted pursuant to them do not have to comply with the provisions of the Constitution. Nor is there anything in the debates which accompanied the drafting and ratification of the Constitution which even suggests such a result. These debates as well as the history that surrounds the adoption of the treaty provision in Article VI make it clear that the reason treaties were not limited to those made in "pursuance" of the Constitution was so that agreements made by the United States under the Articles of Confederation, including the important peace treaties which concluded the Revolutionary War, would remain in effect. It would be manifestly contrary to the objectives of those who created the Constitution, as well as those who were responsible for the Bill of Rights - let alone alien to our entire constitutional history and tradition - to construe Article VI as permitting the United States to exercise power under an international agreement without observing constitutional prohibitions. In effect, such construction would permit amendment of that document in a manner not sanctioned by Article V. The prohibitions of the Constitution were designed to apply to all branches of the National Government and they cannot be nullified by the Executive or by the Executive and the Senate combined.
- Reid v. Covert, 354 U.S. 1 (1957)
Article VI
... This Constitution, and the Laws of the United States which shall be made in Pursuance thereof; and all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land;
"There is nothing in this language which intimates that treaties and laws enacted pursuant to them do not have to comply with the provisions of the Constitution."
Gong! Thanks for playing, but no, you'll have to re-read Article 6 again. You failed the first time through.
Note carefully that there is a semicolon after "This Constitution, and the Laws of the United States which shall be made in Pursuance thereof;". This means that the laws passed by Congress *MUST* be made pursuant to our Constitution. Then, after the clear semicolon, treaties are next stated to be the supreme law of our land alongside our Constitution: "all Treaties made, or which shall be made, under the Authority of the United States, shall be the supreme Law of the Land."
Article I, Section 8
"Clause 11: To declare War, grant Letters of Marque and Reprisal, and
make Rules concerning Captures on Land and Water; "
Notice that Congress is given full authority by our Constitution to make its own laws concerning all captures on land and water.
HINT: That's precisely what Congress did when it ratified the Geneva Conventions.